In wind turbine systems known in the art, sudden changes in the velocity of the wind that acts on the rotor of the wind turbine causes its tower to sway back and forth and sideways. Such, oftentimes circle-like, oscillation of the wind turbine tower is known to significantly shorten the technical life period of the tower, and also to produce significant mechanical load in the yaw system and gearing.
Such oscillations can be still dramatically increased in cases of variable speed turbines, in which certain rotational speeds can cause oscillations that match the tower resonant frequency.